1. Field of the Invention
The field of the invention embraces cam action locking mechanisms for telescoping tubes. Related devices have been employed particularly with extension poles for paint applicators.
2. Description of the Prior Art
The most pertinent prior art known to the inventor are the patents to Burton et al, U.S. Pat. No. 3,596,946, and Pharris, U.S. Pat. No. 3,380,097.
Burton et al disclosed a cam lock disposed in the interior of telescoping tubes. The use of this device is limited or prohibited in applications where it is desirable to utilize the interior of the tubes as, for example, with internally fed paint applicators. This device also has the limitation that in order to tighten or release the tubes it is necessary to rotate the tubes themselves relative to one another as opposed to merely rotating parts of the locking mechanism. With some applications, particularly painting, this limitation can lead to mess and confusion.
Pharris disclosed a threaded locking mechanism that is complex in construction, and cumbersome and difficult to operate. For example, this device requires as much as a full turn and considerable tightening pressure to lock the telescoping tubes relative to one another. On the other hand, the camming action of the present invention by use of greater leverage inherent in its multiple cam construction permits the tightening of the tubes with significantly less pressure exertion and only about a half of a turn or less of the collars.
Other cam locking mechanisms for telescoping tubes have been disclosed in the prior art. However, nothing therein suggests the construction of the present invention or its advantages.